Walking beam oven for advancing products at different speeds in different sections of the oven

ABSTRACT

At least two successive assemblies are formed by respective walking beams and actuatable independently of one another to advance articles through an oven, with a respective hydraulic jack connected to each of the assemblies for horizontally displacing each assembly. A respective pump is connected to each of the jacks in a respective circuit having two sides, with a respective nonreturn valve provided on one of the sides of each of the circuits between each jack and the respective pump. A pair of distributors are provided in the other side of one of the circuits between one of the jacks and the respective pump, with a respective distributor provided in each of the sides of the other circuit between another of the jacks and the respective pump, and hydraulic lines connecting the distributors of the circuits. A retractable stop is provided on one of the assemblies and is selectively engageable with the other assembly, the distributors being controllable to define a first mode of operation wherein the circuits are disconnected from one another and each of the pumps drives the respective jack and the stop is retracted so that the assemblies operate independently to advance the articles, and a second mode of operation wherein the circuits are coupled through the distributors and the jacks are connected in series to only one of the pumps through the distributors and the nonreturn valves, so that with the stop engaged with the other assembly, the assemblies push one another and are thereby synchronized for joint advance of the articles.

CROSS-REFERENCE TO RELATED APPLICATION

This is a National Phase application of PCT/FR86/00264 filed July 24,1986 and based upon French national application No. 85 11 569 filed July24, 1985.

FIELD OF THE INVENTION

The present invention relates to ovens with walking beams in which thewalking beams form at least two successive assemblies mechanicallyindependent of each other and each being movable by means of a hydraulicjack connected to one or more supply pumps. These ovens enable productsto be heated to be advanced at different speeds in the two regions ofthe oven corresponding to the two assemblies, which is advantageous forexample when the oven is loaded partially with hot products coming fromcontinuous casting.

BACKGROUND OF THE INVENTION

When the oven is used in a way in which the two assemblies of beams areto move articles at the same speed, it is difficult to ensure perfectsynchronization between the two assemblies, because of mechanical,electronic or hydraulic imperfections, leaks in the jacks for example.This lack of synchronization results in subjecting the supports to veryhigh forces and to displace the products during heating, which causesdifficulties during removal from the oven and may even cause overlappingof these products.

To overcome this drawback it has been proposed to provide, on the onehand, means for coupling the two beam assemblies together and, on theother hand, logic control means for providing synchronized operation ofthe jacks. But the ovens thus constructed are complicated.

OBJECT OF THE INVENTION

The present invention has as an object an oven with mobile beams of theabove mentioned type but in which the synchronized movement of the twoassemblies of beams is obtained by simple means.

SUMMARY OF THE INVENTION

The oven with walking beams of the invention is characterized in thatone of the assemblies of beams comprises a retractable stop able to comeinto contact with the other assembly so that each of these assembliesmay push the other, and in that the supply means for the jacks comprisedistributers enabling a circuit to be set up comprising in series one ofthe supply pumps, the control jack for one of the assemblies, thecontrol jack of the other assembly and a nonreturn valve.

When the distributors are disposed so as to form the above circuit andwhen the stop has been brought to its active position, the liquiddelivered by the pump actuates the jack of the first assembly, whichpushes back the second assembly through the medium of the stop. Thenonreturn valve generates a counter pressure which brakes the movementof the second assembly so that the stop carried by one of the assembliesremains in contact with the other assembly.

The oven may comprise more than two beam assemblies, in which case eachbeam assembly except one has a retractable stop which may come intocontact with one of the adjacent beam assemblies and the distributorsallow a circuit to be formed in comprising series the assembly of thecontrol jacks.

BRIEF DESCRIPTION OF THE DRAWING

One embodiment of an oven with walking beams will be described hereafterby way of non limitative example, with reference to the accompanyingdrawings in which:

FIG. 1 is a diagrammatic view showing the oven when the two beamassemblies move independently according to the invention; and

FIG. 2 is a view similar to FIG. 1, showing the oven when the twoassemblies move in synchronism.

SPECIFIC DESCRIPTION

Such as is shown in the drawings, the walking beam oven of the inventionincludes a frame 1a for unloading the oven and a frame 1b for loadingthe oven. Each of these frames comprises beams 2 which are movablehorizontally on a bed 3 and may be moved on this bed by a jack 4a or 4b.Bed 3 may itself be moved both vertically and horizontally on fixedramps 5 by means of jacks 6.

Jack 4a is connected to a reversable pump 7a by means of pipes 8a and 9ain which an exchange block 10a is inserted; furthermore, a valve 11a isinserted in pipe 8a whereas a valve 12a and two distributors 13a and 14aare inserted in pipe 9a, the valve 12a being disposed between the twodistributors 13a and 14a. Similarly, jack 4b is connected to a pump 7bby two pipes 8b and 9b in which an exchange block 10b is inserted. Avalve 11b and a distributor 14b are inserted in pipe 8b whereas a valve12b and a distributor 13b are inserted in pipe 9b.

The distributors 13a, 14a, 13b and 14b may occupy positions in whicheach of the pumps 7a and 7b is connected respectively to the jack 4a or4b (FIG. 1). A pipe 15 connects the distributors 14a and 15b togetherand these distributors may occupy positions in which pump 7a is isolatedfrom pipe 9a and is placed in communication with pipe 8b through pipe15, this pipe 8b being isolated from pump 7b, as shown in heavy lines inFIG. 2. A pipe 16 connects the distributors 13a and 13b together andthese distributors may occupy positions in which the ends of pipes 9aand 9b connected to jacks 4a and 4b are placed in communication witheach other through pipe 16, while being isolated respectively from pump7a and from pump 7b. This pipe 16 is connected to a leak compensationcircuit including a pump 17, a check valve 18 and a valve 19.

On the oven unloading frame 1a is fixed a double acting jack 20 whichactuates a retractable stop which may come into abutment against theoven loading frame 1b. This jack 20 is connected to a pump 22 through adistributor 23.

In FIG. 1, the distributors 13a, 14a, 13b and 14b are in their positionsin which jacks 4a and 4b are connected respectively to pumps 7a and 7b,and the piston rod 21 forming the stop is moved away from frame 1b.Thus, the two oven unloading and loading frames 1a and 1b moveindependently of each other.

In FIG. 2, the distributors 13a, 13b, 14a, 14b are in their positions inwhich one of the sides of the jack 4a is connected to the opposite sideof jack 4b through pipe 16, pump 7a being connected to the other twosides of these jacks 4a and 4b. The distributor 23 has been actuated sothat the rod 21 of jack 20 is in contact against the oven loading frame1b.

Under these conditions, the two frames 1a and 1b move strictly insynchronism. For advancing them, pump 7a delivers to jack 4b the oilwhich flows freely through the distributors 14a and 14b, the exchangeblock 10b, and valve 11b. Frame 1b pushes frame 1a back through themedian of the abutting rod 21 and jack 20. The oil of jack 4a flowsthrough valve 11a which is calibrated to a value for retaining andbraking the movement of the frames. Part of the oil returns to thereservoir by flowing through the exchange block 10a and the remainingpart returns to pump 7a; this latter draws in through its replenishingcheck valves the volume which it lacks.

For moving the frames backwards, it is sufficient to reverse thedirection of operation of pump 7a. The oil is then forced into jack 4aand frame 1a moves back while pushing back the frame 1b. The oil fromjack 4b flows through valve 11b, which like valve 11a, is calibrated soas to brake the return movements of the frames.

Both during the advance of the frames and during the retreat thereof,oil flows from one of the jacks 4a and 4b to the other, through pipe 16,but this circuit is at very low pressure.

It goes without saying that the present invention must not be consideredas limited to the embodiment described and shown but covers on thecontrary, all variants thereof, one of which consists of using only asingle pump for driving the "motor" jack and to brake in a closedcircuit on the second jack, after isolating its corresponding pump.

I claim:
 1. A walking beam oven, comprising:at least two successiveassemblies formed by respective walking beams and actuatableindependently of one another to advance articles through an oven; arespective hydraulic jack connected to each of said assemblies forhorizontally displacing each assembly; a respective hydraulic pumpconnected to each of said jacks in a respective circuit having twosides; a respective nonreturn valve provided on one of said sides ofeach of said circuits between each jack and the respective pump; a pairof distributors provided in the other side of one of said circuitsbetween one of said jacks and the respective pump; a respectivedistributor provided in each of said sides of the other circuit betweenanother of said jacks and the respective pump; hydraulic linesconnecting said distributors of said circuits; and a retractable stopprovided on one of the assemblies and selectively engageable with theother assembly, said distributors being controllable to define a firstmode of operation wherein said circuits are disconnected from oneanother and each of said pumps drives the respective jack and said stopis retracted so that said assemblies operate independently to advancesaid articles, and a second mode of operation wherein said circuits arecoupled through said distributors and said jacks are connected in seriesto only one of said pumps through said distributors and said nonreturnvalves, so that with said stop engaged with said other assembly, saidassemblies push one another and are thereby synchronized for jointadvance of said articles.